IMPROVEMENTS IN OR RELATING TO PREFORMED BUILDING MATERIALS

Abstract: A method of forming a preformed building element by applying a protective coating to a substrate such as hydrocarbon-based foams where the protective coating comprises cement and/or sand, and an acrylic polymer.

Description: Improvements in or relating to Preformed Building Materials TECHNICAL FIELD This invention relates to building materials, and to methods of improving their characteristics by applying a surface coating. For convenience only, the present invention will be described with reference to building materials such as panels used in cladding structures such as wall, and roof panels, and in particular panels made from hydrocarbon based foams for which the invention may be particularly applicable. However, it is to be understood that it is not to be limited as such. Moreover, because the invention may have other applications it is to be understood that the prior art and possible embodiments of the invention as discussed below are given by way of example only. BACKGROUND ART Conventionally panels used in buildings for cladding structures are protected/finished and/or reinforced by a surface layer of a material such as paint, fibreglass polyester or epoxy resin, plaster, concrete/cement and the like. Paint is the most commonly used material for finishing and weather proofing wood based materials, plaster is used on softer gib- board type materials or with laths but is not generally suitable for exterior surfaces, while concrete/cement is commonly used for finishing external surfaces of cladding materials such as wood, brick or hydrocarbon based foam panels. With concrete/cement finishes a suitable material such as a mesh may be attached to the surface to improve bonding to the surface. Due to the weight and fragile nature of the cement coating this must generally be applied once the panel has been installed in position. The application operation is thus vulnerable to weather conditions and there is a requirement for skilled on site labour, especially when special finishes or curved surfaces such as at corners or around pillars are required. This adds to the cost and construction time. Furthermore, since the coating is applied after the panel has been attached to support members, the coating relies solely on adhesion to the substrate and is thus susceptible to debonding. Fibreglass polyester or epoxy resin finishes provide a very tough light weight flexible finish and are commonly used with wood based materials. However due to the cost of the epoxy resin this method is not generally economical for large surface areas. Furthermore, polyester resins tend to dissolve hydrocarbon based foam materials making them unsuitable for this application. Certain paints which do not dissolve the foam, such as plastic (acrylic) paints may be applied to the surface to provide a certain amount of improvement in strength and weather resistance to the foam panel, however the amount of protection provided is generally not sufficient for building panels. Although additional strength may be provided by applying a thick layer of paint with a reinforcing mesh such as a fibreglass cloth embedded therein, if applied thickly such paints require a considerable time to harden. Furthermore, the cost of the paint makes the process expensive. There is thus a need for a surface finish for building materials/panels J: which can be applied off site, and in particular for af surface finish that is suitable for finishing hydrocarbon based foam panel materials or attaching cladding to foam materials, which is flexible and tough and which can set in thick applications. Materials such as mixtures of acrylic modifier PRIMAL® FM-2727 supplied by Rohm & Haas Ltd mixed with a Portland cement are known for their ability to set in thick applications even under water, and are used for applications such as repairing and sealing around foundations which may even be under water. These mixtures depend for their setting ability on the complementary setting characteristics of cement and acrylic, the cement taking up moisture to set and the acrylic giving up moisture. They are therefore not dependent on the atmospheric moisture/drying for setting and can thus be applied thickly. Since they have a high percentage of cement and/or sand they provide a relatively low cost repair medium, and are tough and weatherproof. These materials however have not heretofore been used or considered for large scale application as a surface treatment for building materials, or for use as adhesives with foam materials. It is an object of the present invention to provide a method of treating a surface of a building material using a material such as an acrylic modifier/filler mix such as that described above, so as to address the above problems or at least to provide the public with a useful choice. Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only. DISCLOSURE OF THE INVENTION In the broadest sense the present invention provides protective coating for application to material comprising cement, and/or sand or -.nother filler and an acrylic polymer. The invention provides a method of forming a preformed building element characterised by applying a protective coating to a substrate comprising cement and/or sand or another filler and an acrylic polymer in layers and progressively building up the coating until the desired coating thickness has been reached. The substrate can be a hydro-carbon based foam. The protective coating can be provided with a reinforcing material. The reinforcing material can be a flexible lath. The acrylic polymer can include polym ethyl acrylate. The acrylic polymer can be a polymer consisting of Cι-18 alkyl acrylates. The acrylic polymer can be a polymer consisting of Cι-18 alkyl methacrylates. The acrylic polymer can be of the structure; . 1* -*? - 9 o' 1 Rl can consist of one or more of hydrogen, methyl, ethyl, butyl or other suitable aliphatic hydrogen chains. 2 can consist of hydrogen and/or methyl. Rl can be mainly comprised of methyl groups with R2 being hydrogen. The substrate can be provided with a longitudinal cavity to facilitate bending of the element. The cavity can be V-shaped. The cavity can be dish shaped. The method can include the step of applying a protective coating on one surface and a layer of building paper on the opposite surface. The filler material may include glass beads, ceramic bubbles, chalk, quartz, perlite marble, silica sands, natural stone or synthetic filling agents. The reinforcing material may be polypropolene, glass, nylon, metal, carbon, Olefin, or plastics materials of general or specific forms. With a material such as the material described above, since the material is relatively inexpensive compared to epoxy resins, it can provide a low cost alternative treatment for building panels and the like. Furthermore, since it is relatively light in weight, is flexible, and does not dissolve foam type materials, it can be used for coating foam panels off site. The panels can then be fitted to a building structure without the need for further surface treatment once installed. The installation operation is thus not vulnerable to weather conditions, and there is not the requirement for skilled on site labour. Also since attachment members such as nails pass through the panels there is not the tendency for debonding of the surface coating. Furthermore, the panels can be cut and shaped off site as required. Due to the flexible nature of the coating (which can be determined by mixture ratios) the panels can also be bent on installation and if sharp corners are required, the rear of the panel may be relief cut to enable a sharp bend to be made such as for a corner portion. The foam coated material may also be formed in a variety of shapes for different building applications. For example coated half cylindrical shapes may be made for fitting over posts to provide a pillar, or corner pieces may be made for fitting between panels at corners. Imitation finishes such as of brick, wood, weather board, rough cast concrete and the like, may be formed on the surface of panels of a variety of materials by applying the matrix material to a flat or pre-shaped surface, and then working the matrix material as required prior to setting. Reinforcing similar to the front coating, or of other materials such as building paper may also be adhered to the rear surface of the foam panels. This would negate the requirement for on site installation of building paper. The panels could also be used as an alternative to gib- board lining and could have the final paint/wallpaper applied in the factory. With suitable reinforcing, roof tiles and the like incorporating a foam type substrate may be possible. Panels could also be made with an exterior finish on one side and interior finish on the other side and fitted to a building structure, for example with a simple "I" type connector between the panels to provide a joint, thus enabling cladding of a building to be done in a short time. Panels suitable for complete sections such as wall or fence panels may also be possible. For example a thick foam panel may be made with cavities to take roof supports or fence supports, or to form moulds for pouring concrete support pillars. That may provide for roof support. This may be prepared and coated with the matrix material off site, and then quickly assembled at the site, without the need for skilled on site labour. Alternatively or in addition with wall panels, these may be made with extra reinforcement bands laid into the matrix over the panels to give the required strength for roof support. Suitable material clad with the matrix cladding may also be formed with cavities for encasing objects such as existing structural members (i.e. pillars), or. for setting in position and then pouring a material such as concrete into the cavity to form a structural member. Furthermore, a method of construction may be applied to the construction of complete structures made up using a substrate material such as polystyrene which is then completely or partially encased with the matrix . Due to the insulation properties and ease of forming of the substrate, and the excellent water resistant properties of the coating, this method of construction may be suitable for the manufacture of articles such as letter boxes, pillars, beams, posts, and containers. Since the matrix material is flexible and tough and adheres strongly to foam materials, it may also be suitable as an alternative to metal cladding used particularly for cool store panels. The matrix material could be easily repaired if damaged, and moisture content of the foam substrate could be easily checked by simply inserting a probe through the coating material, and subsequently repairing with a suitable material. The strong adhesive properties of the matrix material also make it suitable as an adhesive for attaching foam panels to objects such as a supporting structure. Panels could thus be bonded in position rather than using pins and the like thereby avoiding the need to puncture the foam material and leave it vulnerable to moisture absorption and contamination. The tough flexible nature of the coating may also make it suitable for coating floor and decking materials, and for coating materials for use in fencing and as fence panels. The excellent water proofing properties of the matrix may make it preferable as a coating for exterior surfaces, compared to conventional plaster coatings and the like. A variety of types of the above described matrix material may be used depending on requirements provided they enable a tough flexible coating of relatively low cost suitable for application to building materials. For example the proportions and types of materials used in the flexible modifier PRIMAL® FM-2727 may be varied as required or desired, and additives such as fire retardants may be added, or other fillers used. In coating the surface of the building material, additional coatings of different materials may also be applied as required or desired. For example the surface may first be coated with a thin priming coat of a suitable material prior to applying the matrix material. Alternatively or in addition, further coats of other material may be applied over or between layers of the matrix material. For example material such as treated wood chips, or spherical light weight ceramic or polystyrene bubbles may be used as a filler to lighten the coating material, or may be sprinkled on the surface between coatings to provide additional bulk. The matrix material may be applied by any suitable means. For example it may be spread by hand, brush, or rolled with a roller, sprayed on, or applied by dipping the panel in the matrix material. Any suitable type of reinforcing material may be applied to the surface provided this is able to bond with the material and has sufficient strength. For example a glass fibre material may be most suitable however other fibrous materials such as KEVLAR® or carbon fibres or polyester fibres may be used. The reinforcing material may be applied in any suitable form such as a mat (unidirectional open weave mesh) or as chopped strand. Chopped strand may provide a greater impact resistance for certain applications due to the ability of the fibres to align with the loading direction in the flexible matrix material. In the case of chopped strand application, the reinforcing material may be applied together with the matrix material. Working of the reinforcing into the matrix may be by any suitable method such as pressing, rolling, brushing, surface pressure or vibration, or by the addition of further matrix material, extrusion or vacuum processes. Additional matrix material may be applied over the first coat. This material may be the same as that of the first coat or may be different. Various types of building material may be suitable for treatment by the above method. For example, polystyrene insulation in sheet form or profiled, light weight concrete panels, timber panels, asbestos, cement fibre boards, composites of the above including some insulating or fire retarding materials. In treating the surface of the building material, a first coat of either epoxy, polyurethane, or acrylic, mixed with a hardener may be applied. In a preferred embodiment an all acrylic modifier of the type PRIMAL® FM2727 as supplied by Rohm & Haas Ltd may be suitable. A possible mixture ratio for this may be 100 parts of PRIMAL® FM2727 modifier and 100 parts of Portland cement conforming to ASTM C-150. If required to aid in production, additional cement may be added along with other ingredients such as #70 grade mesh sand, strengthening fibres, thickener, defoamer, coalescing agent, surfactants and dispersants, plasticisers, water, colorants, mica and white cement as required or desired. In the case of an alkali resistant glass mat reinforcement for the above modified cement mix, this may vary in weight and density. For example 115gm/m 2 gives a moderately light weight reinforcement, whilst 2 layers of 115gm/m 2 or a layer of 250gm/m 2 or even two layers of 250gm/m 2 gives much stronger reinforcement. For general foam wall applications an alkali resistant fibre glass mat of 130gm/m 2 may be most suitable. If a second coat matrix is applied this can be either a similar mix to the first coat matrix described above or can be made differently to provide different surface characteristics. For example, the second matrix may comprise 100 parts of PRIMAL® FM2727 flexible modifier to 200 parts of Portland cement conforming to ASTM C-150. If desired this could also have combinations of the same additional ingredients as the first coat matrix described above. Additional layers of the above matrix mixes and reinforcing may be applied in association with a reinforcing material such as alkali resistant glass of woven mesh open construction form (unidirectional alkali resistant reinforcing mesh of open weave) having varying weights from 100gm/m 2 to 600gm/m 2 or more depending on reinforcement requirements. Surface finishes may be carried out in the factory or on site. Typical finishes may include, textures, drag type scratching finishes, trowel smooth finishes, formed or profiled finishes to obtain either very smooth or predetermined finishing shapes and patterns, coloured finishes, painted finishes, sponged or special effect finishes. An example of a special effect finish may be achieved with a mixture of 100 parts of sand type #50 mesh , 30 parts of Portland cement to ASTM C-1500, 10 parts of PRIMAL® FM2727 modifier, and water as required. To this could be added a range of, or all of, the combinations of additional ingredients as included in the matrix coat mixtures described above. Various methods may be used for jointing/sealing the panels on site once installed, and for treating the edges of the panels. To ensure against any seepage into the panels up through the bottom edges additional back wrapping of the panels may be carried out by using a layer of the matrix material with reinforcing as required. The edges of the panels to be joined may be simply butt jointed together, or joined using edge strips with or without a backing rod and sealant, and a reinforcing fabric such as strips of alkali resistant glass mat may be cut to an appropriate width and attached across the joint with a coating of the above matrix material, or some other adhesive or plaster. Alternatively the edges may be tongue and grooved, slotted, ship-lapped, or straight or bevelled or tapered to take a jointing strip such as a plastic or aluminium "I" or "T" jointing strip. Joints may also be covered with battens such as with Tudor type buildings. BRTEF DESCRIPTION OF THE DRAWINGS Further aspects of the present invention will become apparent from the ensuing description which is given by way of example only and with reference to the drawings accompanying the provisional specification in which: Figure 1: is a schematic plan view of foam panel illustrating a building material according to the present invention and its method of treatment, and Figure 2: is a schematic plan view of corner piece for a building illustrating another building material according to the present invention, and Figure 3: is a perspective view of preformed corner building elements of the present invention, and Figure 4: is a sectional view of a corner construction in accordance with the present invention, and Figure 5: is a side perspective view of a typical wall construction using the building elements of the present invention, and Figure 6: is an end view of a eyebrow building element of the present invention, and Figure 6a: illustrates a fixing detail inclusive of the eyebrow element of Figure 6, and Figure 7: illustrates a number of alternative shapes for building elements of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION Having regard to Figure 1, there is shown a schematic sectional view of a panel generally indicated by arrow 1 comprising a polystyrene foam substrate 2 coated with fibre glass reinforced coating generally indicated by arrow 3. The coating 3 consists of a first layer 4 of a material, a layer of alkali resistant glass fibre mat 5, a second layer 6 of a matrix material, a sprinkling of sand and optionally a finishing coat of paint 7. The first layer 4 matrix material is made using a mixture of approximately 100 parts by weight of acrylic flexible modifier PRIMAL® FM-2727 and 180 parts by weight of cement. The second layer 6 matrix material is of similar composition to that of the first layer 4 matrix material with additional sand. A rear surface 8 of the substrate 2 is covered with a layer of building paper 9 which is adhered to the substrate 2 with a coating of the matrix material of similar composition to that of the layer 4. The panel 1 is attached to a supporting structure 10 by means of nails 11. The heads of the nails are covered over with a material similar to that of the matrix material of the second layer 6. The panel 1 shown in this embodiment is provided with the fibre glass reinforced coating 3 off site. Since the reinforced coating 3 is light in weight and flexible, the panel 1 can then be easily transported to the site and fitted into position on the supporting structure 10, without the possibility of damage to the surface as would be the case with a cement coated foam panels. In treating the surface of the foam substrate 2, the matrix material 4 is first applied by rolling, spraying or otherwise a mixture of the matrix onto the substrate 2. The fibre glass mat 5 is then laid over the layer of matrix 4 and pressed in with rollers so that the matrix material permeates between the fibres of the mat 5. A coating of a second matrix material 6 is then applied by spraying and sanding with #70 grade sand, and the panel allowed to dry and subsequently painted as required. Drying may be by air drying but other methods such as snap heating with infra-red radiation dehumidifying or oven curing may be used. A finishing coat of paint is then sprayed on the panel ready for transport to the site for installation. After nailing the panel in position on site the nail heads are covered over with a thin layer of a similar matrix material. Figure 2 shows another embodiment of the present invention in the form of a corner fitting 20 for a building. In this figure components similar to those of the first embodiment are indicated with the same numeral and description is omitted. The corner fitting 20 is used at corners of buildings, and differs from the panel of Figure 1 in that a notch has been cut in the rear of the panel after manufacture so that the panel can be bent though 90°. Due to the flexible nature of the fibre glass reinforced coating 3, this does not crack on bending, enabling curved corner sections to be formed by simply notching the foam and bending, either on site or as pre-formed factory corner pieces. With respect to Figures 3 and 4, the corner element illustrated is provided with a longitudinal V-shaped cut-out 13 in the substrate material 2 which enables sections of the element to be folded at right angles and fixed to corner structure elements 14 as indicated. The cut-out 13 can be dish- shaped which is more suitable for fixture to curved structures. Figure 5 of the drawings illustrates fixture of the corner elements of Figure 3 to a corner structure (as shown in Figure 4) and adjoining panel elements 1 fixed to wall structure members 15. Figures 6 and 6a show an eyebrow element 16 and its method of fixture to a frame structure 17. Figure 7 shows alternative cross-section of the building elements in the form of "mouldings", for trimming and finishing using the elements of the present invention. All of the elements described can be nailed, stapled and/or glued in place. I believe the advantages of my invention to be as follows, however it should be appreciated that all such advantages may not be realised on all embodiments of the invention, and the following list is therefore given by way of example only as being indicative of potential advantages of the present invention. Furthermore, it is not intended that the advantages of the present invention be restricted to those of the list which follows. 1. The matrix material treatment enables panels such as foam type panels for buildings to be made up off site and then installed without the need for further finishing or with only minimal finishing. Panels can therefore be made in a continuous production process with reduced wastage. Problems relating to delays due to weather conditions and the like are thus avoided, skilled on site labour is not required, and rapid construction is possible enabling reduction in construction costs. 2. Higher quality can also be ensured through factory quality control. For example accurately curved surfaces and flat surfaces can be easily produced. Also conformity of production conditions can be ensured so the products can be manufactured under optimum conditions, with materials meeting required standards. 3. Wastage of materials can be avoided since materials can be made to the required size and shape in the factory so that minimal cutting and forming is required on site. 4. Low cost light weight polystyrene foam panels can be used in a wide range of applications since the matrix material does not tend to dissolve polystyrene foams. Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof as defined in the appended claims.

Claims: CLAIMS; 1. A method of forming a preformed building element characterised by: applying a protective coating to a substrate comprising cement and an acrylic polymer in layers and progressively building up the coating until the desired coating thickness has been reached. 2. The method of claim 1 wherein the substrate is a hydro-carbon based foam. 3. The method of claim 1 or claim 2 wherein the protective coating is provided with a reinforcing material. 4. The method of claim 1 wherein the reinforcing material is a flexible lath. 5. The method of claim 1 or claim 4 wherein the acrylic polymer includes polymethyl acrylate. 6. The method as claimed in claims 1 to 5 wherein the acrylic polymer is a polymer consisting of Ci-18 alkyl acrylates. 7. The method of claims 1 to 6 wherein the acrylic polymer is a polymer consisting of Cι-18 alkyl methacrylates. 8. The method of claims 1 to 7 wherein the acrylic polymer is of the structure; Ro i i n ,C -0 -R, 9. The method of claim 8 wherein Rl consists of one or more of hydrogen, methyl, ethyl, butyl or other suitable aliphatic hydrogen chains. 10. The method of claims 7 or 8 wherein R2 consists of hydrogen and/or methyl. 11. The method claimed in any one of claims 8 to 10 wherein Rl is mainly comprised of methyl groups with R2 being hydrogen. 12. The method claimed in any one of claims 1 to 11 wherein the substrate is provided with a longitudinal cavity to facilitate bending of the element. 13. The method claimed in claim 12 wherein the cavity is V-shaped. 14. The method of claim 13 wherein the cavity is dish shaped. 15. The method of claimed in any one of claims 1 to 14 including a protective coating on one surface and a layer of building paper on the opposite surface. 16. A preformed building element comprising a substrate and a protective coating on the surface thereof, said protective coating including major portions of cement and an acrylic polymer. 17. A preformed element as claimed in claim 16 wherein the substrate is a hydro-carbon based foam. 18. A preformed element as claimed in claim 16 or claim 17 wherein the protective coating is provided with a reinforcing material. 19. A preformed element as claimed in claim 16 wherein the reinforcing material is a flexible lath. 20. A preformed element as claimed in claim 16 to 19 wherein the acrylic polymer includes polym ethyl acrylate. 21. A preformed element as claimed in claims 16 to 20 wherein the acrylic polymer is a polymer consisting of Cι-18 alkyl acrylates. 22. A preformed element as claimed in claims 16 to 21 wherein the acrylic polymer is a polymer consisting of Ci-18 alkyl methacrylates. 23. A preformed element as claimed in claims 16 to 22 wherein the acrylic polymer is of the structure; >2 -- ■ <- - ?* ■ . tf c -o. Rl 24. A preformed element as claimed in claim 23 wherein Ri consists of one or more of hydrogen, methyl, ethyl, butyl or other suitable aliphatic hydrogen chains. 25. A preformed element as claimed in claims 22 or 23 wherein R2 consists of hydrogen and/or methyl. 26. A preformed element as claimed in any one of claims 23 to 25 wherein Rl is mainly comprised of methyl groups with R2 being hydrogen. 27. A preformed element as claimed in any one of claims 16 to 26 wherein the substrate is provided with a longitudinal cavity to facilitate bending of the element. 28. A preformed element as claimed in claim 27 wherein the cavity is V- shaped. 29. A preformed element as claimed in claim 28 wherein the cavity is dish shaped. 30. A preformed element as claimed in any one of claims 16 to 29 including a protective coating on one surface and a layer of building paper on the opposite surface. 31. A method of forming a preformed building element characterised by: applying a protective coating to a substrate comprising sand and/or a filler material and an acrylic polymer in layers and progressively building up the coating until the desired coating thickness has been reached. 32. The method of claim 31 wherein the substrate is a hydro-carbon based foam. 33. The method of claim 31 or claim 32 wherein the protective coating is provided with a reinforcing material. 34. The method of claim 31 wherein the reinforcing material is a flexible lath. 35. The method of claim 31 or claim 34 wherein the acrylic polymer includes polymethyl acrylate. 36. The method as claimed in claims 31 to 35 wherein the acrylic polymer is a polymer consisting of Ci-18 alkyl acrylates. 37. The method of claims 31 to 36 wherein the acrylic polymer is a polymer consisting of Cι-18 alkyl methacrylates. 38. The method of claims 31 to 37 wherein the acrylic polymer is of the O- structure; . ? » -O -R! 39. The method of claim 38 wherein Ri consists of one or more of hydrogen, methyl, ethyl, butyl or other suitable aliphatic hydrogen chains. 40. The method of claims 37 or 38 wherein R2 consists of hydrogen and/or methyl. 41. The method claimed in any one of claims 38 to 40 wherein Ri is mainly comprised of methyl groups with R2 being hydrogen. 42. The method claimed in any one of claims 31 to 41 wherein the substrate is provided with a longitudinal cavity to facilitate bending of the element. 43. The method claimed in claim 42 wherein the cavity is V-shaped. 44. The method of claim 43 wherein the cavity is dish shaped. 45. The method of claimed in any one of claims 31 to 44 including a protective coating on one surface and a layer of building paper on the opposite surface. 46. A preformed building element comprising a substrate and a protective coating on the surface thereof, said protective coating including major portions of sand and/or a filler material and an acrylic polymer. 47. A preformed element as claimed in claim 46 wherein the substrate is a hydro-carbon based foam. 48. A preformed element as claimed in claim 46 or claim 47 wherein the protective coating is provided with a reinforcing material. 49. A preformed element as claimed in claim 46 wherein the reinforcing material is a flexible lath. 50. A preformed element as claimed in claim 46 to 49 wherein the acrylic polymer includes polymethyl acrylate. 51. A preformed element as claimed in claims 46 to 50 wherein the acrylic polymer is a polymer consisting of Cι-18 alkyl acrylates. 52. A preformed element as claimed in claims 46 to 51 wherein the acrylic polymer is a polymer consisting of Ci-18 alkyl methacrylates. 53. A preformed element as claimed in claims 46 to 52 wherein the acrylic polymer is of the structure; 54. A preformed element as claimed in claim 53 wherein Ri consists of one or more of hydrogen, methyl, ethyl, butyl or other suitable aliphatic hydrogen chains. 55. A preformed element as claimed in claims 52 or 53 wherein R2 consists of hydrogen and/or methyl. 56. A preformed element as claimed in any one of claims 53 to 55 wherein Ri is mainly comprised of methyl groups with R2 being hydrogen. 57. A preformed element as claimed in any one of claims 46 to 56 wherein the substrate is provided with a longitudinal cavity to facilitate bending of the element. 58. A preformed element as claimed in claim 57 wherein the cavity is V- shaped. 59. A preformed element as claimed in claim 58 wherein the cavity is dish shaped. 60. A preformed element as claimed in any one of claims 46 to 59 including a protective coating on one surface and a layer of building paper on the opposite surface.

Inventors: HOLYOAKE IAN CONRAD, HOLYOAKE, IAN, CONRAD
Applicants: HOLYOAKE IAN CONRAD, HOLYOAKE, IAN, CONRAD
Application year: 1994
Main classification: E04C2
IPC codes: C09D133, E04C1, E04C2